My hand book says 20w50 and in spite of modern trends being towards lighter oils, that is what's in it at the moment, but in the mornings it's taking longer and longer to suck it up and put the red light out (maybe 5 seconds or so now)
Now - tomorrow I am going to buy some oil (it uses about a litre a month) so should I:

Stick with the thick stuff so the pump stays primed longer?
or
use thinner stuff that would suck up easier?

(please don't suggest fixing the bearings/pump/anti-drain back valve or whatever - I don't have time to do that so for now it's just a stop gap until I get settled oop norf)